# Changes in the Physical Properties of Calcium Alginate Gel Beads under a Wide Range of Gelation Temperature Conditions

^{*}

## Abstract

**:**

_{1}, 1.2–3.6%, w/v), calcium lactate concentration (X

_{2}, 0.5−4.5%, w/v), gelation temperature (X

_{3}, 5–85 °C), and gelation time (X

_{4}, 6–30 min). Diameter (Y

_{1}, mm), sphericity (Y

_{2}, %), and rupture strength (Y

_{3}, kPa) were selected as the dependent variables. A decrease in gelation temperature increased the diameter, sphericity and rupture strength of the CAG beads. Additionally, the CAG beads prepared at 5 °C exhibited the highest rupture strength (3976 kPa), lowest calcium content (1.670 mg/g wet), and a regular internal structure. These results indicate that decreasing the gelation temperature slows the calcium diffusion rate in CAG beads, yielding a more regular internal structure and increasing the rupture strength of the beads.

## 1. Introduction

_{1}, 1.2−3.6%, w/v), calcium lactate concentration (X

_{2}, 0.5−4.5%, w/v), gelation temperature (X

_{3}, 5–85 °C), and gelation time (X

_{4}, 6–30 min), while diameter (Y

_{1}, mm), sphericity (Y

_{2}, %), and rupture strength (Y

_{3}, kPa) were selected as the dependent variables. In addition, to better understand the relationship between rupture strength of the CAG bead and gelation temperature, calcium and sodium ion contents and microstructures of CAG beads were investigated.

## 2. Materials and Methods

#### 2.1. Materials

_{3}; Quality Control Standard-21 Elements, MA, USA), respectively. All other chemicals and reagents used were of analytical grade.

#### 2.2. Calcium Alginate Gel (CAG) Bead Preparation Method

#### 2.3. Diameter and Sphericity Measurement

^{TM}9.1, IMT i-Solution Inc., Daejeon, Korea) coupled to a stereoscopic microscope (125× magnification; SZX16, Olympus, Tokyo, Japan). The diameter (mm) of the CAG beads was calculated by averaging the shortest and longest diameters, while the sphericity (%) of the CAG beads was calculated as the percentage ratio of the shortest and longest diameters.

#### 2.4. Rupture Strength Measurement

#### 2.5. Experimental Design and Statistical Analysis

^{4}factorial points, 2

^{3}axial points (α = 2), and three replicates of the center point. The independent variables were sodium alginate concentration (X

_{1}, %, w/v), calcium lactate concentration (X

_{2}, %, w/v), gelation temperature (X

_{3}, °C), and gelation time (X

_{4}, min). The ranges of the independent variables and their levels are presented in Table 1. Diameter (Y

_{1}, mm), sphericity (Y

_{2}, %), and rupture strength (Y

_{3}, kPa) were chosen as the dependent variables and the run order of the experiment was randomized to minimize the effect of unexpected variables. The experimental data were analyzed using the response surface regression procedure in Minitab statistical software (Version 16, Minitab Inc., State College, PA, USA) to fit the following generalized quadratic polynomial model Equation (1):

_{0}is a constant, and β

_{i}, β

_{ii}, and β

_{ij}are linear, quadratic, and interaction regression coefficients, respectively. X

_{i}and X

_{j}are coded values of the independent variables. Three-dimensional response surface plots were produced from the fitted response surface model equations using Maple software (Maple 7, Waterloo Maple Inc., Waterloo, ON, Canada).

#### 2.6. Moisture Content

#### 2.7. Calcium and Sodium Ion Content

#### 2.8. Sodium Ions Diffusion of CAG Beads

#### 2.9. CAG Bead Microstructure

#### 2.10. Density

## 3. Results and Discussion

#### 3.1. Fitting the Models

_{1}(diameter) and Y

_{3}(rupture strength) were significant (p < 0.05), whereas the quadratic and interaction terms were not. The constant, X

_{1}, X

_{3}, X

_{1}X

_{1}, and X

_{3}X

_{3}term coefficients for Y

_{2}(sphericity) were significant (p < 0.05), thus implying a curvilinear effect of X

_{1}and X

_{3}on the sphericity of CAG beads, while all interaction terms for Y

_{2}were not significant. The insignificant interaction terms for Y

_{1}, Y

_{2}, and Y

_{3}mean that the effects of gelation temperature on the physical properties of CAG beads were not significantly related to the other factors—sodium alginate and calcium lactate concentration and gelation time. The determination coefficient (R

^{2}) of the fitted quadratic polynomial model equations for Y

_{1}, Y

_{2}, and Y

_{3}were 0.913, 0.912, and 0.935, respectively, and the R

^{2}values for all response surface models were highly significant (p < 0.01) [19]. Furthermore, the adjusted R-square (Adj R

^{2}) values for Y

_{1}, Y

_{2}, and Y

_{3}were 0.811, 0.809, and 0.860, respectively. All R

^{2}and Adj R

^{2}values were greater than 0.8, indicating that the fitted equations adequately describe the effects of the independent variables on the diameter, sphericity, and rupture strength of CAG beads [20,21,22].

_{2}was significant (p < 0.05). Conversely, the square terms of Y

_{1}and Y

_{3}and interaction terms of all dependent variables were insignificant (p > 0.05). The P-values for the lack-of-fit tests of all response surface models were higher than 0.05 (Y

_{1}, Y

_{2}, and Y

_{3}were 0.415, 0.389, and 0.170, respectively), suggesting that the response surface models adequately explained the functional relationship between the dependent and independent variables [24].

#### 3.2. Diameter and Sphericity

_{3}) and other independent variables [sodium alginate (X

_{1}) and calcium lactate (X

_{2}) concentration, gelation time (X

_{4})] on the physical properties of the CAG beads.

_{1}) of the CAG beads increased with increasing sodium alginate concentration (X

_{1}) and decreased with increasing gelation temperature (X

_{3}). The effect of sodium alginate concentration and gelation temperature on the diameter of CAG beads might be explained by the viscosity of sodium alginate, which increased with increasing concentration or decreasing gelation temperature. As viscosity increased, the size of the sodium alginate droplets on the nozzle tip also increased, thereby increasing the diameter of the CAG beads [25,26]. Moreover, it can be seen from Figure 2a that the diameter (Y

_{1}) of the CAG beads decreased when the calcium lactate concentration (X

_{2}) or gelation time (X

_{4}) increased. These results can be explained by the study of Klokk et al. [26], in which the gel network was contracted by diffusing calcium ions into the sodium alginate droplets in the reactor.

_{2}) of the CAG beads increased as gelation temperature (X

_{3}) was slightly increased, and then decreased gradually. This is in contrast to the effect of sodium alginate concentration on the sphericity of CAG beads. CAG bead sphericity is closely related to sodium alginate viscosity; the shape of sodium alginate droplets is significantly altered when they hit the calcium lactate solution surface under low viscosity conditions, but sphericity is recovered by increasing the surface tension and gelation above a certain viscosity [9]. Consequently, the sphericity of the CAG beads gradually improved when sodium alginate viscosity increased (increasing sodium alginate concentration or decreasing gelation temperature); however, if the viscosity is too high, the falling sodium alginate droplets develop tails and the CAG beads eventually become tear-shaped [27]. An increase in the gelation time (X

_{4}) seemed to increase the sphericity of CAG beads slightly; however, the P-value of the X

_{4}term coefficient for sphericity was greater than 0.05 (Table 3). These results suggest that gelation time does not have a significant effect on the sphericity of CAG beads likewise the calcium lactate concentration (X

_{2}). These results indicate that the shape of the falling sodium alginate droplets is an important factor determining the sphericity of CAG beads, and the influence of other factors is not significant after the formation of CAG beads formed through the reaction between alginate and calcium ions. In this study, CAG beads with sphericity greater than 95% were indistinguishable compared to perfect spheres when observed with the naked eye. Thus, preparation conditions must be carefully controlled to produce CAG beads with excellent visual sphericity.

#### 3.3. Rupture Strength

_{3}) of CAG beads increased proportionally with the sodium alginate concentration (X

_{1}), calcium lactate concentration (X

_{2}), and gelation time (X

_{4}). These results are consistent with previous studies that determined CAG gel strength according to the degree of interaction between calcium ions and α-L-guluronic acid, finding that strength was directly proportional to sodium alginate concentration, calcium concentration, and the duration of the interaction between alginate and calcium [28,29,30].

_{3}) of the CAG beads increased when the gelation temperature (X

_{3}) decreased. Some studies have hypothesized that the increase in gel strength with low gelation temperature might be caused by the formation of a more dense internal structure due to a reduced calcium ion diffusion rate [31,32,33]; however, no experimental results or explanations yet support this theory. Consequently, we measured the calcium and sodium ion content of CAG beads prepared at different temperatures (5, 45, and 85 °C). Other factors were set as follows: sodium alginate concentration, 2.4%; calcium lactate concentration, 2.5%; gelation time, 18 min. As shown in Figure 3, the calcium ion content of the CAG beads decreased from 2.627 to 1.670 mg/g wet weight when the gelation temperature decreased from 85 to 5 °C. This means that the diffusion rate of calcium ions into sodium alginate droplets decreases with decreasing gelation temperature. For the same reasons, the sodium ion content of the CAG beads was highest (0.278 mg/g wet weight) when the gelation temperature was 5 °C.

#### 3.4. Microstructure

#### 3.5. Optimal Conditions for Maximum Rupture Strength

_{3}). The optimal X

_{1}(sodium alginate concentration), X

_{2}(calcium lactate concentration), X

_{3}(gelation temperature), and X

_{4}(gelation time) conditions for preparing CAG beads with a maximum rupture strength were 3.6%, 4%, 5 °C, and 30 min, respectively (Table 7). Table 8 shows the percentage error verifying the accuracy of the predicted values under the optimal conditions. The predicted Y

_{1}(diameter), Y

_{2}(sphericity), and Y

_{3}(rupture strength) values were 2.85 mm, 94.5%, and 6676 kPa, respectively. We prepared CAG beads under optimal conditions, yielding similar experimental Y

_{1}, Y

_{2}, and Y

_{3}values of 2.88 ± 0.01 mm, 97.5 ± 0.9%, and 6444 ± 692 kPa, respectively. Consequently, the percentage error values (1.05, 3.17, and 3.48%, respectively) among the experimental and predicted values of Y

_{1}, Y

_{2}, and Y

_{3}were very small, implying that the developed models were considerably fitted [38].

## 4. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 2.**Three-dimensional response surface plots of the physical properties ((

**a**), Diameter; (

**b**), Sphericity; (

**c**), Rupture strength) of CAG beads. X

_{1}, sodium alginate concentration (%, w/v); X

_{2}, calcium lactate concentration (%, w/v); X

_{3}, gelation temperature (°C); X

_{4}, gelation time (min).

**Figure 3.**Calcium (open circles) and sodium ion (filled circles) content of CAG beads prepared at different gelation temperatures.

**Figure 4.**Energy-dispersive X-ray spectrometer (EDS) spectra and mapping results for sodium ions in CAG beads prepared at 5 °C after immersion in distilled water for different lengths of time.

**Figure 5.**Visual appearance and low-vacuum scanning electron microscope (LV-SEM) images of CAG beads prepared at different gelation temperatures.

**Figure 6.**Rupture strength (open circles) and moisture content (filled circles) of CAG beads prepared at different gelation temperatures.

**Table 1.**The range and levels of the independent variables in central composite design (CCD) for monitoring the effects of preparation conditions on the physical properties.

Independent Variables | Symbol | Range and Levels | ||||
---|---|---|---|---|---|---|

−2 | 1 | 0 | 1 | 2 | ||

Sodium alginate concentration (%, w/v) | X_{1} | 1.2 | 1.8 | 2.4 | 3.0 | 3.6 |

Calcium lactate concentration (%, w/v) | X_{2} | 0.5 | 1.5 | 2.5 | 3.5 | 4.5 |

Gelation temperature (°C) | X_{3} | 5 | 25 | 45 | 65 | 85 |

Gelation time (min) | X_{4} | 6 | 12 | 18 | 24 | 30 |

**Table 2.**The CCD matrix and experimental values of the dependent variables for each independent variable.

Run No. | Independent Variables | Dependent Variables | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

Coded Values | Uncoded Values | |||||||||||

X_{1} | X_{2} | X_{3} | X_{4} | X_{1} | X_{2} | X_{3} | X_{4} | Y_{1} | Y_{2} | Y_{3} | ||

Factorial | 1 | −1 | −1 | −1 | −1 | 1.8 | 1.5 | 25 | 12 | 3.07 | 96.7 | 1993 |

portions | 2 | 1 | −1 | −1 | −1 | 3.0 | 1.5 | 25 | 12 | 3.08 | 98.9 | 3473 |

3 | −1 | 1 | −1 | −1 | 1.8 | 3.5 | 25 | 12 | 3.00 | 96.2 | 2274 | |

4 | 1 | 1 | −1 | −1 | 3.0 | 3.5 | 25 | 12 | 3.02 | 98.1 | 4005 | |

5 | −1 | −1 | 1 | −1 | 1.8 | 1.5 | 65 | 12 | 2.82 | 92.1 | 1901 | |

6 | 1 | −1 | 1 | −1 | 3.0 | 1.5 | 65 | 12 | 2.88 | 95.4 | 2629 | |

7 | −1 | 1 | 1 | −1 | 1.8 | 3.5 | 65 | 12 | 2.81 | 91.6 | 2195 | |

8 | 1 | 1 | 1 | −1 | 3.0 | 3.5 | 65 | 12 | 2.87 | 95.7 | 3606 | |

9 | −1 | −1 | −1 | 1 | 1.8 | 1.5 | 25 | 24 | 2.93 | 97.8 | 2420 | |

10 | 1 | −1 | −1 | 1 | 3.0 | 1.5 | 25 | 24 | 2.99 | 99.2 | 3832 | |

11 | −1 | 1 | −1 | 1 | 1.8 | 3.5 | 25 | 24 | 2.91 | 98.3 | 2601 | |

12 | 1 | 1 | −1 | 1 | 3.0 | 3.5 | 25 | 24 | 2.91 | 97.8 | 4500 | |

13 | −1 | −1 | 1 | 1 | 1.8 | 1.5 | 65 | 24 | 2.72 | 94.6 | 1959 | |

14 | 1 | −1 | 1 | 1 | 3.0 | 1.5 | 65 | 24 | 2.77 | 95.5 | 3575 | |

15 | −1 | 1 | 1 | 1 | 1.8 | 3.5 | 65 | 24 | 2.70 | 94.2 | 2087 | |

16 | 1 | 1 | 1 | 1 | 3.0 | 3.5 | 65 | 24 | 2.77 | 95.4 | 3902 | |

Axial | 17 | −2 | 0 | 0 | 0 | 1.2 | 2.5 | 45 | 18 | 2.73 | 89.4 | 1436 |

portions | 18 | 2 | 0 | 0 | 0 | 3.6 | 2.5 | 45 | 18 | 2.99 | 98.5 | 4420 |

19 | 0 | −2 | 0 | 0 | 2.4 | 0.5 | 45 | 18 | 3.14 | 96.6 | 1044 | |

20 | 0 | 2 | 0 | 0 | 2.4 | 4.5 | 45 | 18 | 2.82 | 98.1 | 3414 | |

21 | 0 | 0 | −2 | 0 | 2.4 | 2.5 | 5 | 18 | 3.04 | 98.1 | 3976 | |

22 | 0 | 0 | 2 | 0 | 2.4 | 2.5 | 85 | 18 | 2.62 | 90.7 | 2440 | |

23 | 0 | 0 | 0 | −2 | 2.4 | 2.5 | 45 | 6 | 3.09 | 96.7 | 2065 | |

24 | 0 | 0 | 0 | 2 | 2.4 | 2.5 | 45 | 30 | 2.88 | 97.8 | 3111 | |

Center | 25 | 0 | 0 | 0 | 0 | 2.4 | 2.5 | 45 | 18 | 2.97 | 98.3 | 2788 |

points | 26 | 0 | 0 | 0 | 0 | 2.4 | 2.5 | 45 | 18 | 2.92 | 96.6 | 2942 |

27 | 0 | 0 | 0 | 0 | 2.4 | 2.5 | 45 | 18 | 2.88 | 97.5 | 3110 |

_{1}: Sodium alginate concentration (%, w/v), X

_{2}: Calcium lactate concentration (%, w/v), X

_{3}: Gelation temperature (°C), X

_{4}: Gelation time (min). Y

_{1}: Diameter (mm), Y

_{2}: Sphericity (%), Y

_{3}: Rupture strength (kPa). Each experiment was carried out ten times and the mean value was used.

**Table 3.**The regression coefficients of the fitted quadratic polynomial models for monitoring the effects of preparation conditions on the physical properties.

Parameter | Y_{1} | Y_{2} | Y_{3} | |||
---|---|---|---|---|---|---|

Coefficient | p-Value | Coefficient | p-Value | Coefficient | p-Value | |

Constant | 2.92333 | 0.001 | 97.4667 | 0.001 | 2946.67 | 0.001 |

X_{1} | 0.03542 | 0.011 | 1.3625 | 0.001 | 752.50 | 0.001 |

X_{2} | −0.03792 | 0.007 | 0.0042 | 0.986 | 338.67 | 0.001 |

X_{3} | −0.10042 | 0.001 | −1.8042 | 0.001 | −263.17 | 0.003 |

X_{4} | −0.05292 | 0.001 | 0.4292 | 0.088 | 203.83 | 0.013 |

X_{1}X_{1} | −0.01969 | 0.141 | −0.8198 | 0.006 | 28.04 | 0.713 |

X_{2}X_{2} | 0.01031 | 0.426 | 0.0302 | 0.904 | −146.71 | 0.072 |

X_{3}X_{3} | −0.02719 | 0.050 | −0.7073 | 0.014 | 98.04 | 0.212 |

X_{4}X_{4} | 0.01156 | 0.373 | 0.0052 | 0.983 | −56.96 | 0.459 |

X_{1}X_{2} | −0.00188 | 0.899 | −0.0688 | 0.812 | 101.25 | 0.262 |

X_{1}X_{3} | 0.00937 | 0.528 | 0.2813 | 0.340 | −59.50 | 0.502 |

X_{1}X_{4} | 0.00187 | 0.899 | −0.5313 | 0.085 | 87.00 | 0.331 |

X_{2}X_{3} | 0.01188 | 0.427 | 0.0938 | 0.746 | 4.00 | 0.964 |

X_{2}X_{4} | 0.00187 | 0.899 | 0.0063 | 0.983 | −48.75 | 0.581 |

X_{3}X_{4} | 0.00063 | 0.966 | 0.1063 | 0.714 | −26.00 | 0.767 |

_{1}: Sodium alginate concentration (%, w/v), X

_{2}: Calcium lactate concentration (%, w/v), X

_{3}: Gelation temperature (°C), X

_{4}: Gelation time (min). Y

_{1}: Diameter (mm), Y

_{2}: Sphericity (%), Y

_{3}: Rupture strength (kPa).

**Table 4.**The response surface model equations for monitoring the effects of preparation conditions on the physical properties.

Quadratic Polynomial Model Equations | R^{2} | Adj R^{2} | S | p-Value |
---|---|---|---|---|

Y_{1} = 2.92333 + 0.03542X_{1} − 0.03792X_{2} − 0.10042X_{3} − 0.05292X_{4} − 0.01969X _{1}^{2} + 0.01031X_{2}^{2} − 0.02719X_{3}^{2} + 0.01156X_{4}^{2} − 0.00188X_{1}X_{2}+ 0.00937X _{1}X_{3} + 0.00187X_{1}X_{4} + 0.01188X_{2}X_{3} + 0.00187X_{2}X_{4} + 0.00062X _{3}X_{4} | 0.913 | 0.811 | 0.0577410 | 0.001 |

Y_{2} = 97.4667 + 1.3625X_{1} + 0.0042X_{2} − 1.8042X_{3} + 0.4292X_{4} − 0.8198X _{1}^{2} + 0.0302X_{2}^{2} − 0.7073X_{3}^{2} + 0.0052X_{4}^{2} − 0.0688X_{1}X_{2} + 0.2813X _{1}X_{3} − 0.5313X_{1}X_{4} + 0.0938X_{2}X_{3} + 0.0063X_{2}X_{4} + 0.1063X _{3}X_{4} | 0.912 | 0.809 | 1.13336 | 0.001 |

Y_{3} = 2946.67 + 752.50X_{1} + 338.67X_{2} − 263.17X_{3} + 203.83X_{4} + 28.04X _{1}^{2} − 146.71X_{2}^{2} + 98.04X_{3}^{2} − 56.96X_{4}^{2} + 101.25X_{1}X_{2} − 59.50X _{1}X_{3} + 87.00X_{1}X_{4} + 4.00X_{2}X_{3} − 48.75X_{2}X_{4} − 26.00X_{3}X_{4} | 0.935 | 0.860 | 343.729 | 0.001 |

_{1}: Sodium alginate concentration (%, w/v), X

_{2}: Calcium lactate concentration (%, w/v), X

_{3}: Gelation temperature (°C), X

_{4}: Gelation time (min). Y

_{1}: Diameter (mm), Y

_{2}: Sphericity (%), Y

_{3}: Rupture strength (kPa).

**Table 5.**The analysis of variance (ANOVA) of response surface model equations for monitoring the effects of preparation conditions on the physical properties.

Dependent Variables | Sources | DF | SS | MS | f-Value | p-Value |
---|---|---|---|---|---|---|

Y_{1} Diameter (mm) | Regression | |||||

Linear | 4 | 0.373817 | 0.093454 | 28.03 | 0.001 | |

Square | 4 | 0.040404 | 0.010101 | 3.03 | 0.061 | |

Interaction | 6 | 0.003838 | 0.000640 | 0.19 | 0.973 | |

Residual | ||||||

Lack of fit | 10 | 0.035942 | 0.003594 | 1.77 | 0.415 | |

Pure error | 2 | 0.004067 | 0.002033 | - | - | |

Total | 26 | 0.458067 | - | - | - | |

Y_{2} Sphericity (%) | Regression | |||||

Linear | 4 | 127.095 | 31.7738 | 24.74 | 0.001 | |

Square | 4 | 25.677 | 6.4193 | 5.00 | 0.013 | |

Interaction | 6 | 6.179 | 1.0298 | 0.80 | 0.587 | |

Residual | ||||||

Lack of fit | 10 | 13.967 | 1.3967 | 1.93 | 0.389 | |

Pure error | 2 | 1.447 | 0.7233 | - | - | |

Total | 26 | 174.365 | - | - | - | |

Y_{3} Rupture strength (kPa) | Regression | |||||

Linear | 4 | 19,002,146 | 4,750,537 | 40.21 | 0.001 | |

Square | 4 | 1,093,213 | 273,303 | 2.31 | 0.117 | |

Interaction | 6 | 390,870 | 65,145 | 0.55 | 0.760 | |

Residual | ||||||

Lack of fit | 10 | 1,365,918 | 136,592 | 5.27 | 0.170 | |

Pure error | 2 | 51,875 | 25,937 | - | - | |

Total | 26 | 21,904,022 | - | - | - |

**Table 6.**Rupture strength of CAG beads generated at 5 °C after immersion in distilled water for different periods.

Immersion Time | 0 min | 30 min | 60 min |
---|---|---|---|

Rupture strength | 3910 ± 150 ^{a} | 3784 ± 119 ^{a} | 3187 ± 114 ^{b} |

^{a,b}The same letter indicates no significant difference (p < 0.05, Tukey’s range test).

Optimal Conditions | Y_{3} Rupture Strength (kPa) | |||
---|---|---|---|---|

Target Value | Maximum | |||

X_{1} Sodium alginate concentration (%, w/v) | Coded value | 2 | ||

Actual value | 3.6 | |||

X_{2} Calcium lactate concentration (%, w/v) | Coded value | 1.5 | ||

Actual value | 4 | |||

X_{3} Gelation temperature (°C) | Coded value | −2 | ||

Actual value | 4 | |||

X_{4} Gelation time (min) | Coded value | 2 | ||

Actual value | 30 |

Y_{1} Diameter (mm) | Y_{2} Sphericity (%) | Y_{3} Rupture Strength (kPa) | |
---|---|---|---|

Predicted values | 2.85 | 94.5 | 6676 |

Experimental values | 2.88 ± 0.01 | 97.5 ± 0.9 | 6444 ± 692 |

Error (%) | 1.05 | 3.17 | 3.48 |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Jeong, C.; Kim, S.; Lee, C.; Cho, S.; Kim, S.-B.
Changes in the Physical Properties of Calcium Alginate Gel Beads under a Wide Range of Gelation Temperature Conditions. *Foods* **2020**, *9*, 180.
https://doi.org/10.3390/foods9020180

**AMA Style**

Jeong C, Kim S, Lee C, Cho S, Kim S-B.
Changes in the Physical Properties of Calcium Alginate Gel Beads under a Wide Range of Gelation Temperature Conditions. *Foods*. 2020; 9(2):180.
https://doi.org/10.3390/foods9020180

**Chicago/Turabian Style**

Jeong, Chungeun, Seonghui Kim, Chanmin Lee, Suengmok Cho, and Seon-Bong Kim.
2020. "Changes in the Physical Properties of Calcium Alginate Gel Beads under a Wide Range of Gelation Temperature Conditions" *Foods* 9, no. 2: 180.
https://doi.org/10.3390/foods9020180